Silencer



Sept. 19, '1933. R. J. MacKl-:NzlE ET AL SILENCER Filed Aug. 15, 1930 2 Sheets-Sheet l Patented Sept. 19, 1933 UNITED STATES SILENCER Roy J. MacKenzie and Lucien L. Haas,

Buffalo,

N. Y., assignors to Buffalo Pressed Steel Company, Buffalo, N. Y.

Application August 15, 1930. Serial No. 475,452

14 Claims.

This invention relates to silencers of the kind commonly employed for silencing the exhaust from an internal combustion engine.

The objects of this invention are to provide silencers of this type with pads of sound deadening material in certain portions thereof to improve the silencing eiect; also to provide silencers of this kind including a plurality of shells lform- .ing chambers through which the gases pass in succession, and in which pads of sound absorbing material are used on portions of said shells to overcome the drumming effect produced by the impinging of gases on said shells; also to provide silencers of this kind, in which pads of sound absorbing material are provided in portions of the silencer opposite discharge passages in the shells to reduce noises resulting from the discharge of the gases; also to provide a silencer oi.' this kind having an outer shell provided with a baille intermediate of its end and having a pad of sound deadening material arranged against the side of said baille opposite to that against which the incoming gases impinge; also to provide a silencer of this kind in which the baille in the inner shell is apertured to permit a portion of the gases to pass through said pad; also to provide a silencer of this kind in which an intermediate shell is employed, a portion of which is of elliptical cross section and having pads of sound deadening material arranged in the portions of greater diameter of the elliptical shell; also to improve silencers of this kind in other respects hereinafter specified. .Y

In the accompanying drawings:

Fig. 1 is a longitudinal central section of a silencer embodying this invention;

Figs. 2 and 3 are transverse sections thereof, on lines 2-2 and 3 3 respectively of Fig. 1;

Fig. 4 is a longitudinal central section oi.' a silencer of modied construction;

Figs. 5 and 6 are sections thereof, respectively on lines 5-5 and 6-6 of Fig. 4.

This invention is applicable to silencers of many different' constructions, and in order to illustrate our invention we have shown two different types of silencers provided with the improvements embodying our invention, and it will, of course, be understood that it is not intended to restrict this invention to the constructions shown.

In the construction shown in Fig. 1, the silencer includes an outer shell A and an inner shell B, both of these shells extending throughout the length of the silencer.l head C at the receiving end of the silencer provides shoulders to which the shells may be secured, this head being also formed to provide a tubular extension c to which the exhaust pipe leading from the engine may be connected. At the opposite or discharge end of the silencer is arranged a head D to which the other ends of the shells are secured, and which is formed with a tubular extension d to which a tail or discharge pipe may be secured, or through which gases may be discharged directly to the air.

Between the ends of the inner shell, a baille E is provided which may be suitably secured Within the inner shell and which divides this shell into a gas receiving and a gas discharge chamber. This baille is provided with perforations 10 and the innershell is provided with additional perforations l1, through which gases pass out of the gas receiving chamber of the shell. We have found that a desirable silencing eiect is produced by providing at the back face of the baffle E a cushion or pad of sound deadening material, and in the particular construction shown a pad F is provided. This pad may be made of any noncombustible pneumatic pressure equalizing substance, which has a large number of communicating air spaces therein, which act as pneumatic cushions to deaden the sound of the gases impinging against the baille E. Metal wool has been found very desirable for this purpose, but it is not intended to limit this invention to this material, since asbestos in brous form, mineral wool, or other substances may be used in place of metal wool. The pad, in the particular construction shown, is arranged Within a small cylinder 12 suitably secured or mounted in the discharge chamber of the inner shell, the cylinder shown being mounted on the baille E and having its other end closed by means of a cap or disk 14. The cylinder 12 ls preferably provided with apertures 15, and consequently a small portion of the gases entering the` receiving chamber pass through the perforations 10 of the baille and through the pad F and perforations 15 directly into the discharge chamber oi. the silencer. It is not, however, necessary to provide for a passage of the gases through the pad F, since if the cylinder 12 were imperforate, a similar silencing effect would be produced.v The space betwen the inner and outer shells A and B is divided by an annular partition or bafile G, the inner and outer edges of which are respectively secured to the shelves B and A. The baille or partition G has apertures 17 therein through which the gases may pass into a chamber 18, from which they pass through holes 19 in the inner shell B to enter into the discharge chamber in this shell.

The space between the partition or baille G and the head C is, in the construction shown, divided into two silencing chambers by means of a tapering shell H, the smaller end of which engages the inner shell B and-is' suitably secured to the head C. The largerl end of this shell is secured to a shoulder 20 of the baille or partition Gr, and preferably this shoulder is elliptical in form, so that the larger end of the shell H is of elliptical cross section.

A material reduction in the noise of the exhaust can be effected if the gas is discharged from the receiving chamber into the next adjacent chamber against pads or pneumatic pressure equalizing substances, and by making a portion of the intermediate shell elliptical, such pads can be located in the wider portions of the shell where they will produce the least restriction of the passages for the gas. i

In the construction illustrated, therefore, we have provided pads I, which are arranged in those portions of the shell H which are adjacent to the ends of the elliptical cross section through which the greatest diameter passes, and the discharge openings l1 in the inner shell B are so arranged that the gases discharged therethrough impinge against these pads. By means of the arrangement described, the pads produce the silencing effect upon the gases which would otherwise be discharged against the shell H, and by arranging these pads in the ends of the elliptical cross section, the portion of the chamber 21 into which these gases discharge from the receiving chamber of the inner shell is not materially reduced in cross section, so that no material increase in back pressure results. The pads I may be of the same or similar material as the pad F, and the material is confined in its correct position by,

means of two plates 23 of perforated metal, which plates may be suitably spot welded, or otherwise secured to the shell H. By means of the arrangement described, an economic use is made of the sound deadening material'which results not only in a saving of material, but enables these pads to be used in the silencer without increasing the size thereof, and without restricting the gas passages of the chamber 21.

The gases are discharged from the chamber 21 through a series of apertures 25 arranged in the portion of the shell beyond the pads I. The gases, .after passing through the apertures 25, enter into a chamber 26, from where they can pass through the apertures 1'7 in the baille or partition G, and consequently pass out of the silencer, as already described.

We have found that in silencers'some noises commonly called ldrumming result from the impinging of jets or streams of gas against an outer shell of the mulller or silencer. We have also found that this drumming effect can be eliminated or reduced so as to render it unobjectionable by the use of a pad or lining of sound deadening material arranged within these shells, so that the radially discharged gases impinge upon these pads or linings. In order to prevent this drumming and to further reduce noises of the exhaust, another pad or lining K of suitable sound absorbing material ls provided adjacent to the inner wall of the outer shell A and adjacent to the discharge apertures 25 in the shell H. This pad K may be cylindrical in form and ts snugly against the inner wall of lthe shell A, and is preferably held in place by means of a shell 27 of perforated material. Prem ferably, this shell 27 is also tapered or frustoconical in form so as to extend approximately parallel to the shell H. This arrangement provides a practically uniform space for the gases between the p'ad or lining K and the shell H, and also provides for an increased thickness of the pad adjacent to the bafile C, so that drumming effect against this baille is also prevented. By lining only that portion of the outer shell against which gases impinge with the sound-deadening material, the gas passages within the silencer are not materially restricted, and a considerable portion of the outer shell contacts directly with the gases, resulting in a more rapid cooling of the same.

In the case of both of the pads I and K, in addition to eliminating or materially reducing the usual drumming eifect, a material silencing of the noises of the exhaust is effected by the provision of these pads, preferably'due to a certain amount of pressure equalizlng effect produced by the pads, permitting gases to flow into the air spaces in these pads when a sudden flow of gas enters the silencer, and then again permitting this gas to discharge out of the air spaces in the pads between explosions or gas discharges. It will be noted that this same silencing effect is produced by means of the pad F, which is arranged in such a manner that the gases discharging from the chamber 18 through the apertures 19, impinge against the perforated cylinder l2 in which the pad F is arranged.

Holes or openings 28 in the inner shell near the receiving end thereof serve to prevent darnage to the silencer incase of explosions within the muffler and permit a small flow of gas in the chamber 21 in a direction contrary to the main flow of gas.

In the construction shown in Figs. 4 to 6 inclusive, outer and inner shells A1 and B1 are secured at their ends to heads C1 and D1, in the manner described in connection with Figs. l to 3, and a baille E1 is provided, which divides the inner shell into a receiving and discharge chamber. A pad F1 in rear of the baille E1 and made of suitable sound deadening material is, in this construction, confined in a chamber in the inner shell arranged between the baille E1 and a second baille 30. The baille E1 contains perforations through which a portion of the gases entering the receiving chamber may pass to the pad F1, and the sides of the shell B1, which confine this pad, are provided with apertures through which some of the gases entering the pad may pass. The head 30 is also provided with apertures through which some of the gas which has passed through the pad F1 may enter directly 'into the discharge chamber of the silencer.

The portion of the inner shell which encloses the gas receiving chamber is provided with apertures 33, through which most of the gases discharge against the pad or lining K1 upon entering the chamber between the inner and the outer shell, the pad K1 being confined in its operative position by means of a cylinder 34 of perforated metal, and by means of an annular end wall 35 suitably secured to the outer shell.

The space between the inner and outer shells of this silencer is divided into two chambers by the tapered shell 38 and the outer shell A1.

charge chamber within this shell, from where' they are discharged from the silencer.

Silencers embodying this invention as illustrated in both structures shown, are' so constructed that they are not solely dependent upon the action of the pneumatic pressure equalizing substance to be useful, since sufficient muiiling chambers are provided toy ensure a fairly satisfactory muiiling effect even if the metal wool or other material becomes burned out or filled with soot or carbon.

We4 claim as our invention:

1. A silencer including an outer shell, a shell l arranged within said outer shell and forming therewith a passage for gases and having discharge openingsv therethrough through which gases discharge outwardly toward said outer shell for flowing in said passage, and a layer of metal wool arranged adjacent to that portion of the inner surface of said outer shell toward which said gases are discharged and into which a portion of said gases may penetrate, and a shell of perforated metal confining said metal wool between said-last mentioned perforated shell and said outer shell.

2. A silencer including outer and inner cylindrical shells forming between them a passage for gases, said inner shell being arranged to receive incoming gases at one end thereof and having a perforated baille intermediate of its ends against which incoming ga'ses impinge, a cushion of non-combustible fiber-like material arranged on the side of said baiile opposite to that on which incoming gases impinge, and. which has a silencing effect on said gases and permits a portion thereof to pass therethrough, and openings in said inner shell through whichA the remainder of the gases are discharged therefrom into said passage and from said passage into said inner shell beyond said cushion.

3. A silencer including an inner and an outer shell, a baille arranged intermediate of the ends of saidl inner shell and` dividing the same into a gas receiving and a gas discharge chamber, av pad of non-combustible fiber-like material in said discharge chamber adjacent to said baffle, said baffle having perforations in the portion thereof adjacent to said pad to permit a portion of the incoming gases to discharge through said pad, and openings in said inner shell at both sides of said baffle to permit the remaining gases to fiow out of the receiving chamber of said inner shell and into the discharge chamber thereof.

4. A silencer including an inner and an outer shell arranged to form between them a space for gas, a baiiie arranged intermediate of the ends of said inner'shell and dividing the same into a gas receiving and a gas discharge chamber, a pad of non-combustible fiber-like material in said discharge chamber adjacent to said baflie, said bafiie having perforations in the portion thereof adjacent to said pad to cause said pad to produce a silencing effect on said incoming gases, and openings in said inner shell at opposite sides of said baille. to permit gases to flow outwardly from the receiving chamber of said inner shell into said space between said inner and outer shells, and then into the discharge chamber of said inner shell.

5. A silencer having inner and outer shells arranged to form between them a space for gas, a baffle intermediate of the ends of said inner shell to divide the inner shell into a receiving chamber and a discharge chamber, said baille A having perforations therethrough, a pad of sound absorbing non-combustible material arranged on the discharge sideof said baille, openings in said inner shell at both sides of said bafile to permit gases to discharge outwardly from said receiving chamber into said space between said inner and outer shells, and then into said discharge chamber, and a pad of non-combustible soundabsorbing material arranged about and spaced from the portion of the inner shell from which gases are discharged outwardly, to cause said gases to impinge against said last mentioned pad.

6. A silencer having inner and outer shells arranged to form between them a space for gas, a baffle intermediate of` the ends of said inner shell to divide the inner shell into a receiving chamber and a discharge chamber, said baffle having perforations therethrough, a pad of sound absorbing non-combustible material arranged on the'discharge side of said baffle, openings in said inner shell at both sides of said ballie to permit' gases to discharge outwardly from said receiving chamber into said space between said inner and outer shells, and then into said discharge chamber, a. pad of non-combustible sound absorbing material arranged about and spaced from the portion of the'inner shell from which gases are discharged outwardly, to Vcause said gases to impinge against said last mentioned pad, a chamber in which said first mentioned pad is confined, and perforations in a wall of said last mentioned chamber to permit a part of the gases from the receiving chamber to pass through said pad into said discharge chamber.

7. A silencer including a shell, a second shell arranged about said first shell and having a portion thereof spaced at a greater distance from said inner shell than other parts thereof, a pad of sound absorbing material in said spaced portion, and discharge openings in the inner shell arranged to direct jets of gases toward said pad.

8. A silencer including a shell, a second shell arranged about said first shell and having a portion thereof of substantially elliptical cross section, a pad of sound absorbing material in'a' porlil() tion of greater diameter of said elliptical portion,

and gas discharge orifices in the inner shell arrangedto direct gas jets toward said pad.

9. A silencer including innerand outer substantially cylindrical shells, an intermediate tapering shell arranged between the inner and outer shells, a pad of sound absorbing material in the portion of said intermediate shell of greater diameter, a pad of sound absorbing material arranged on said outer shell opposite the portion of lesser diameter of said intermediate shell, and discharge apertures in said inner and intermediate shells arranged to deflect gases discharged therethrough against said pads.

10. A silencer including an inner and an outer shell arranged to form between them a space for gas, a bafiie arranged intermediate of the ends of said inner shell and dividing the same into a gas receiving and a gas discharge chamber, a pad of sound absorbing material arranged against said the silencer, to silence gases impinging against said baille, and openings in said inner shell at said -receiving and discharge chambers thereof to permit gases to flow from said receiving chamber into said space between said shells and from said space into said discharge chamber, the openings leading into said discharge chamber being arranged to cause gases to impinge against said pad.

1l. A silencer including an inner and an outer shell arranged to form between them a space for gas, a baille arranged intermediate of the ends of said inner shell and dividing the same into a gas receiving and a gas discharge chamber, a pad of sound absorbing material arranged against said baille at the side thereof opposite to the inlet of the silencer, to silence gases impinging against said baille, and openings in said inner shell at said receiving and discharge chambers thereof to permit gases to ow from said receiving chamber into said space between said shells and from said space into said discharge chamber, the openings leading into said discharge chamber being arranged to cause gases to impinge against said pad, said baille having openings arranged to permit a restricted quantity of said gases to ilow through said pad directly into said discharge chamber.

12. A silencer including inner and outer shells arranged to form between them a space for gas, a baille arranged intermediate of the ends of said inner shell and dividing the sameV into a gas receiving and a gas discharge chamber, a pad of sound absorbing material arranged within said inner shell at the discharge side of said baille,

`said baille having perforations therein in the portion thereof adjacent to said pad, said inner shell having discharge openings for permitting gas to discharge from said receiving chamber mancia into said space between said shells and from said space into said discharge chamber, and openings in said inner shell for permitting portions of said gases passing through said pad to discharge into said space.

l3. A silencer having inner and outer shells spaced apart to form a space for gases between the shells, a pair of perforate baffles in said inner shell, a pad of sound absorbing material; arranged between said perforate bafes, and with said baffles dividing said shell into gas receiving and discharge chambers, and openings in said inner shell at the receiving and discharge chambers thereof to permit gases to flow from said receiving chamber to said discharge chamber through said space between said shells, a portion of said gases flowing from. said receiving to said discharge chamber through said perforate baffles and pad.

14. A silencer having inner and outer shells spaced apart to form a space for gases between the shells, a pair of perforate baiiles in said inner shell, a pad of sound absorbing material arranged between said perforate baffles, and with said bailles dividing said shell into gas receiving 100 and discharge chambers, openings in said inner shell at the receiving and discharge chambers thereof to permit gases to flow from said receiving chamber to said discharge chamber through said space between said shells, a portion of said gases flowing from said receiving to said discharge chamber through said perforate bailles and pad, and perforations in the portion of said inner shell which confines said pad to cause a part ot the gases ilowing through said pad to discharge 110 into said space between said shells.

ROY J. MACKENZIE. LUCIEN L. H AAS. 

